Bomb lab warms up diesel technology

turbo washing

I wonder how many young engineers have been told to open the valve on the Turbo charging washing line and then to get the fright of their lives when the 6 foot diameter wheel spinning at close to 10,000 rpms "Surges"

Walnut shells are being used as a blasting (cleaning) material along with foam balls, sand, grit, volcanic dust depending on the material to be cleaned.

...and so you now know that water comes out of the aftercooler

How many "general yachting" (since that is the category here) vessels have 6 foot turbine wheels turning at 10K?

Hi,

The yachts are getting bigger so one never knows what will be next and what will be required to power it and whatever it is will most likely be turbocharged so anything is possible.

Progress

I think you will find that the equipment, electronics and machinery start life on the ships and then are either adopted or changed slightly to move onto yachts.

So what we saw 20 years ago on ships you are seeing on yachts nowadays.

Improving exhaust valve life is a good thing, but that's really tough to do with ceramics. Their brittle nature means that some will work fine and others will fracture for no apparent reason. There have been some ceramic success stories in turbines, but they have been few and far between. Been there, done that, got the T shirt.. In small turbines it may actually be easier, since the shock loading isn't there, but trying to get a valve in a high speed engine to work. There's also a bigger % payoff in applying the technology to turbine, which is why the DoE is interested in the application of ceramics to small turbines. My company is under a DoE contract to do a ceramic turbine rotor test this year and even if you design it very carefully, then you have to make the parts (very difficult and expensive) and the cost of ceramic powder prices have lately gone thru the roof.

The real problem is that high speed diesels are only about 35% efficient (and yes, I know big, huge 2 cycle diesels are more efficient, but a practical size diesel in a boat like we are talking about here is going to be a lot closer to 35% than 45%). What is happening is that about 30% of the energy is going out in cooling of the engine (both oil and water) and the other 35% is going out of the exhaust.

There isn't much heat that you can recover from the cooling system. The water is only around boiling, and you can't efficiently recover heat that is that cool and do any useful work from it.

The exhaust is hotter, but by the time it goes through the turbocharger it is less than 1,000 degrees F and even if you could capture it with a 25% efficient waste heat recovery system, you are looking at an 8.75% improvement in fuel consumption. Considering the weight, initial cost and and maintenance of the waste heat recovery system, that's not going to ever pay off the initial investment.

A gas turbine, otoh, is somewhat less efficient to start with, but since all the waste heat goes out the exhaust, theres almost twice as much energy that can be recovered. Gas turbine waste heat recovery systems are currently being investigated by the Navy for systems as small as 4MW, and the amount of power gained can be about 25% of the base engine power. That would be a system that would supply an additional megawatt of power when put behind a 4MW system. To put it another way, if you can cut your fuel bill by 25% for a destroyer or cruiser, that's a lot of fuel.

I think you will see more of these combined cycle systems in the near future and they will shrink in sized down to something that will eventually find civil applicaton

Pratt & Whitney developed "Carboblast", soft walnut shells, for cleaning turbines in the 1950's You can still put that kind of stuff down older turbines, but newer engines have tiny laser drilled holes in the combustor and airfoils that would be clogged in seconds with that much junk going thru an engine. Water washing is mostly used now, even on big commercial engines to clean the junk out of compressors. Plain water can be used at low speeds to clean up the first few stages while the engine is running, but it boils off and in the later stages doesn't do much good. For a complete cleaning they motor the engine on the starter and then inject a mixture of cleaners and then the engine is cleaned that way. Also solid carbon dioxide is another thing that seems to work well, and won't clog small passages.

All of this stuff goes back to the "adiabatic diesel engine" that was the big talk a while ago... except they forgot that lubricants burn at the temperatures they wanted to run at, and things that would be lubricants at that temperature are solid at room temp.....

I was just looking at the links in the first post and there were pics of SiN, ceramic valves... SiN is tough stuff, but I'm not so sure I'd like to make valves out of it... It took us a long time to get geometry that we felt would work on a turbine, and we gave up some tip speed to do it, but you don't know until you run it..

What was the old John Denver song.. "some day's are diamonds, some days are stones" The good day's are when your proposal gets accepted and you win a big program, that says your concept was a good idea and you get to prove it... Or when something works in the test cell, no problem getting pumped up for that. But then, six months later when you're fighting to keep awake at 3:00 in the afternoon if you screwed up and had too big a lunch...

I think on the largest of yachts, we will see more of a trend of Diesel electric with pods, like their larger cousins (the cruise ships) are using and have been using with good results.